Method of forming workpieces by abrading

ABSTRACT

A peripheral recess is formed in a cylindrical mounting portion of a metal workpiece. A flat is then formed in the peripheral recess. A set screw is adapted to bear against the flat when the mounting portion is positioned in a chuck. The workpiece is then hardened. The cylindrical mounting portion is then finished to a predetermined diameter by centerless grinding.

United States Patent 1191 111 3,811,234 Soares, Jr. May 21, 1974 [54]METHOD OF FORMING WORKPIECES BY 3,626,644 12/1971 Cupler 51/288 ABRADING3,298,140 1/1967 Enyeart.... 51/103 R 3,732,648 5/1973 Schaller 51/103 R[75] Inventor: Edward W. Scares, .lr., New

Bedford, Mass.

[73] Assignee: Gulf & Western Precision Primary Examiner-Donald G; KellyE i i C Mancheser, Attorney, Agent, or Firm-Charles l. Sherman Mass.

[22] Filed: Oct. 19, 1972 [21] Appl. No.: 298,940 [57] ABSTRACT [52]U.S. Cl...-. 51/323, 51/288, 51/289 R, A P p a r s is m d in aylindrical mount- 51/327 ing portion of a metal workpiece. A flat isthen formed [51] Int. Cl. B24b 3/06, B24b 5/22 in the peripheral recess.A set screw is adapted to bear 58 Field of Search 51/103 R, 288, 289 R,323; against the flat when the mounting Portion is P 51 /327 tioned in achuck. The workpiece is then hardened. The cylindrical mounting portionis then finished to a [56] Referen s Cit d predetermined diameter bycenterless grinding.

UNITED STATES PATENTS 2.718.689 9/1955 Mason 51/288 UX 6 Claims, 7Drawing Figures METHOD OF FORMING WORKPIECES BY ABRADING BACKGROUND OFTHE INVENTION This application relates to workpieces and a method ofmaking same. The invention is particularly applicable to cutting toolsand will be described with particular reference thereto. However, itwill be appreciated that the invention has broader applications and maybe used for other types of tools or the like.

Cutting tools commonly have a cylindrical mounting portion which isreceived in a chuck. A flat is provided on the cylindrical mountingportion. A set screw threaded on the chuck is adapted to bear againstthe flat for holding the cylindrical mounting portion against rotationrelative to the chuck.

Tools of the type described are commonly formed by machining a piece oftool steel to the rough shape desired. The flat is also machined intothe cylindrical mounting portion. The tool is then hardened. Afterhardening, at least the cylindrical mounting portion must be ground to aprecise diameter so that it will closely fit within a chuck. In previousarrangements, the cylindrical mounting portion was rough ground oversizeby centerless grinding. The flat in the cylindrical mounting portionpresentsa peripheral discontinuity in the cylindrical'rnounting portion.During centerless grinding, this peripheral discontinuity causes unevenpressure against the peripheral surface of the cylindrical mountingportion. For example, when the flat is in the area of the work restblade on the centerless grinder, the pressure against the cylindricalmounting portion on opposite sides of the flat is greater than when theflat 'is away from the work rest blade. Likewise, when the flat isagainst the grinding wheel the pressure between the grinding wheel andthe surfaces of the cylindrical mounting portions on opposite sides ofthe flat is greater. This makes it extremely difficult, if notimpossible. to obtain precise diameters by centerless grinding. There ischanging pressure on the workpiece as it rotates past the backup wheel,the grinding and the work rest blade. This successive variation inpressure on the workpiece causes certain areas to be ground away morerapidly than others so that the cylindrical portion would take onsomewhat of an oval shape. The peripheral discontinuity also causes thegrinding wheel to wear unevenly and it must be dressed frequently.

In previous arrangements, thecylindrical mounting portion of the toolwas rough ground oversize by centerless grinding because this is themost economical and rapid way of grinding a cylindrical workpiece to arough diameter. The too] then had to be mounted in a cylindrical grinderbetween centers for finish grinding the cylindrical mounting portion toa predetermined finish diameter.

SUMMARY around the entire peripheral surface of the cylindrical mountingportion. Therefore, there is no variation in pressure as the workpiecerotates between the backup wheel, grinding wheel and work rest blade.Grinding action occurs on substantially true cylindrical surfaces sothat accuracy is highly improved.

It is a principal object of the present invention to provide an improvedmethod for finish grinding a metal workpiece.

It is also an object of the present invention to provide an improvedmethod for finish grinding a cylindrical mounting portion of a tool.

It is an additional object of the present invention to provide animproved tool having an improved cylindrical mounting portion thereon.

It is a further object of the present invention to provide a method ofmanufacturing a tool which is less expensive than existing procedures.

It is another object of the present invention to provide an improvedmethod of grinding a cylindrical mounting portion of a workpiece to apredetermined diameter within very close tolerances.

BRIEF DESCRIPTION OF THE DRAWING The invention may take form in certainparts and arrangements of parts, a preferred embodiment of which will bedescribed in detailin this specification and illustrated in theaccompanying drawing which forms a part hereof.

FIG. 1 is an elevational view showing a prior art type of tool;

FIG. 2 is a plan view looking generally in the direction of arrows 2-2of FIG. 1;

FIG. 3 is an elevational view of an improved tool constructed inaccordance with the present invention;

FIG. 4 is a view similar to FIG. 3 and showing the tool after a furtherstep in the manufacturing procedure;

FIG. 5 is a plan view looking generally in the direction of arrows 5-5of FIG. 4;

FIG. 6 is a side elevational view showing the improved too] of thepresent invention mounted in a centerless grinder; and

FIG. 7 is a plan view looking generally in the direction of arrows 7-7of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,wherein the showings are for purposes of illustrating a preferredembodiment of the invention only and not for purposes of limiting same,FIG. 1 shows a prior art type of cutting tool A. Tool A is formed fromtool steel and includes a cylindrical mounting portion 12. Cylindricalmounting portion 12 terminates at spaced-apart opposite end portions 14and 16. Cutting edges for a drill, end mill or the like are adapted tobe formed on opposite end portions 18 and 20 of tool A.

A fiat surface 22 is formed into cylindrical mounting portion 12. Flatsurface 22 has opposite arcuate sides 26 and 28. Sloping shoulders 32and 34 slope from sides 26 and 28 down to flat surface 22. Flat surface22 lies in a plane extending parallel to'the longitudinal axis ofcylindrical mounting portion 12. Flat surface 22 is formed intocylindrical portion 12 so that it terminates short of the longitudinalaxis of tool 12. Therefore, spaced-apart opposite edges 36 and 38 offlat surface 22 extend over an arc of around l50 on the outer pe- 3ripheral surface of cylindrical mounting portion 12. it will berecognized that this are is immaterial and flat surface 22 may be formedto any desirable depth into cylindrical mounting portion 12 as long assufficient material remains to insure strength and rigidity.

With a prior art tool machined to the shape described, the tool is thenhardened. After hardening, it is necessary to grind cylindrical mountingportion 12 to a desirable predetermined cylindrical diameter so that itwill closely fit within a mounting chuck. The most efficient and leastexpensive manner of grinding cylindrical mounting portions to a precisediameter is by centerless grinding. When tool A is positioned in acenterless grinder, flat surface 22 presents a peripheral discontinuityon outer cylindrical surface 12. In any given position of tool A in thecenterless grinder, the peripheral discontinuity caused by flat surface22 causes different pressures to be brought against different outerperipheral surfaces of cylindrical mounting portion 12. For example, ascylindrical mounting portion 12 is rotating past grinding wheel withflat surface 22 facing the grinding wheel, only those cylindricalportions between edges 14 and 26, and 16 and 28, are bearing against thegrinding wheel. However, the backup wheel is bearing across the entireouter periphery of cylindrical mounting portion 12 between edges 14 and16 op posite flat surface 22. This causes a greater pressure to beexerted on the peripheral surface portions between edges 14 and 26, and16 and 28. When flat surface 22 is rotating past the backup wheel, thepressure .of the backup wheel is greater on those peripheral surfacesextending between edges 14 and 26, and 16 and 28. However, the pressureof the grinding wheel is uniform across the entire peripheral surface ofcylindrical.

mounting portion 12 between edges 14 and 16 opposite flat surface 22.Therefore, the grinding action which takes place on the peripheralsurface portion opposite to flat surface 22 has a lower per unitpressure thanthat exerted against the peripheral surface when flatsurface 22 is passing the grinding wheel. This difference in pressure onthe peripheral surfaces of cylindrical mounting portion 12 makes itextremely difficult, if not .impossible, to hold a desired cylindricaldiameter within'close tolerances by centerless grinding. Therefore, itis necessary to only rough centerless grind to oversize diameter and tothen mount the tool in a cylindrical grinder between centers foraccurately grinding cylindrical mounting portion 12 to a cylindricaldiameter within close tolerances.

In accordance with the present invention, a cutting tool B is machinedfrom tool steel to the rough shape shown in FIG. 3. Tool B has acylindrical mounting portion C which actually comprises two spaced-apartcylindrical mounting portions 40 and 42. Cylindrical mounting portion Chas longitudinally-spaced-apartopposite edges 44 and 46. Opposite endportions 48 and 50 on tool B are adapted to be formed into cutting edgesor the like. A cylindrical peripheral recess D is machined intocylindrical mounting portion C. Peripheral recess D is preferablycentrally located between opposite ends 44 and 46 of cylindricalmounting portion C. Peripheral recess'D has spaced-apart opposite edges52 and 54 which also respectively define opposite edges for cylindricalmounting portions 40 and 42. Peripheral recess portion D has a diameteronly slightly less than the outer diameter of cylindrical mountingportion C so that cylindrical mounting portion C retains its strengthwhile providing peripheral recess D with a peripheral surface which isbelow the outer peripheral surface of cylindrical mounting portion C.

Flat surface 60 is then formed in peripheral recess portion D. Flatsurface 60 has spaced-apart arcuate edges 62 and 64 which are alsospaced inwardly from edges 52 and 54 of peripheral recess D. Shoulders66 and 68 slope inwardly toward one another from edges 62 and 64 tointersect flat surface 60. Flat surface 60 is substantially centrallylocated between opposite edges or shoulders 52 and 54 of peripheralrecess D, and also substantially centrally located between opposite ends44 and 46 of cylindrical mounting portion C.

It will be recognized that opposite portions 48 and 50 of tool B definecutting body portions which have a diameter substantially less than thediameter of cylindrical mounting portion C. Cutting edges generallyindicated at 70 and 72 may be formed on cutting body portions 48 and 50.Cutting edges for an end mill are shown. However, it will be recognizedthat many different types of cutting edges or tool edges may be formedon opposite body portions 48 and 50. In the arrangement described, flatsurface 60 lies in a plane extending parallel to the longitudinal axisof tool B. Flat surface 60 is also machined into peripheral recessportion D so that its opposite edges 74 and 76' extend over an arc ofaround l50 on the outer periphery of peripheral recess D. It will berecognized that flat surface 60 may be machined into peripheral recess Dto extend over any desirable arc. It is simply necessary that flatsurface 60 be sufiiciently wide so that a set screw will have adequatebearing thereagainst to firmly hold cylindrical mounting portion Cwithin a chuck.

Instead of forming a cutting tool having two opposite bodies 48 and 50,it will be recognized that body 50 may be omitted so that cylindricalmounting portion C would terminate at end 46. Cylindrical mounting portion C would then simply extend between opposite ends 44 and 46, andhave one body 48 extending therefrom. End 46 would then simply be flat.A tool having working ends at both of the opposite ends thereof isdescribed merely for simplicity of description. However, it will beappreciated that the invention also covers cutting tools and formationthereof when only one working end is provided. 4

Subsequent to machining of the tool as described, the tool is hardened.Subsequent to hardening, it is necessary to finish grind cylindricalportion C to a predetermined diameter within very precise tolerances.With peripheral recess portion D, cylindrical mounting portion Cincludes two spaced-apart substantially perfectly cylindrical surfaces40 and 42. Peripheral recess D provides a discontinuity around theentire peripheral surface of cylindrical mounting portion C. Therefore,

there is no re-occurring discontinuity as described with respect to theprior art tool. Uneveness of pressure during centerless grinding doesnot exist because grinding takes place on two perfectly cylindricalsurfaces having no short discontinuity therein.

Tool B may then be positioned in a plunge-type centerless grinderincluding a rotatable cylindrical grinding wheel E and a rotatablecylindrical backup wheel F. A work rest blade G positioned betweengrinding wheel E and backup wheel F below the axes of rotation thereofprovides an upwardly facing surface 80 on which tool B rests. Backupwheel F forces tool B substantially constant. This makes it possible tocenterless grind cylindrical portions 40 and 42 to a very precisediameter within very close tolerances bycenterless grinding. In thearrangement shown, grinding wheel E and backup wheel F have a width toextend completely across cylindrical mounting portion C between oppositeends 44 and 46 thereof.

It will be recognized that tool B may also be mounted in a differenttype of centerless grinder for finish grinding of body portions 48 and50 for finishing of the cutting tool edges. The plunge-type ofcenterless grinder for finish grinding cylindrical portion C has beengenerally shown because it is what forms the basis of the presentinvention. In the preferred arrangement, cylindrical mounting portion Cis finish ground to a finish diameter between 8 and 14 thousandthsgreater than the diameter of peripheral recess D. Furthermore, it hasbeen found that it is possible to finish cylindrical mounting portion Cby centerless grinding to a diameter which does not deviate from that ofa perfect cylinder by more than 0.0005 inch.

lt is possible to achieve roundness tolerances within 0.0001 inch if sodesired. The grinding action on cylindrical mounting portion C is brokenup by providing peripheral recess D so that the grindability ratio goesup. More workpieces can be finish ground per dressing of the grindingwheel. It is also possible to use harder grinding wheels so that life ofthegrinding wheel is increased. A higher productivity is achieved withthe present invention because down-time hours of the grinder will begreatly decreased.

Although the invention has been shown and described with reference to apreferred embodiment, it will be recognized that equivalent alterationsand modifications will occur to others skilled in the art upon thereading and understanding of this specification. The present inventionincludes all such equivalent alterations and modifications and islimited only by the scope of the claims.

Having thus described my invention, I claim:

1. A method of finishing a metal workpiece having a longitudinal axisand a cylindrical mounting portion comprising the steps of; forming aperipheral recess in said cylindrical mounting portion to provide acylindrical recess portion having spaced-apart shoulders and a diameterless than said cylindrical mounting portion, forming a flat surface insaid recess portion lying in a plane parallel to said longitudinal axis,hardening said workpiece, and finishing said cylindrical mountingportion to a predetermined diameter by centerless grinding.

2. The method of claim 1 wherein said cylindrical mounting portion hasopposite ends and said step of machining said recess is carried out bymachining said recess at a location substantially centrally between saidopposite end portions.

3. The method of claim 2 wherein said recess has spaced-apart shouldersand said step of forming said flat surface is carried out forming saidflat surface at a location substantially centrally between saidshoulders to a width less than the distance between said shoulders.

4. The method of claim 1 wherein said workpiece comprises a tool havinga cutting body portion integral with said mounting portion, and furtherincluding the step of forming said cutting body portion to a diameterless than the diameter of said mounting portion and forming cuttingedges on said body portion prior to said step of hardening saidworkpiece.

5. The method of claim 1 wherein said step of finishing said cylindricalmounting portion is carried out by centerless grinding of said mountingportion to a finished diameter between 8 and I4 thousandths greater thanthe diameter of said cylindrical recess portion.

6. The method of claim 1 wherein said step of finishing said'cylindricalmounting portion is carried out by centerless grinding of saidcylindrical portion to a diameter which does not deviate from that of aperfect cylinder by more than 0.0005 inch.

1. A method of finishing a metal workpiece having a longitudinal axisand a cylindrical mounting portion comprising the steps of; forming aperipheral recess in said cylindrical mounting portion to provide acylindrical recess portion having spaced-apart shoulders and a diameterless than said cylindrical mounting portion, forming a flat surface insaid recess portion lying in a plane parallel to said longitudinal axis,hardening said workpiece, and finishing said cylindrical mountingportion to a predetermined diameter by centerless grinding.
 2. Themethod of claim 1 wherein said cylindrical mounting portion has oppositeends and said step of machining said recess is carried out by machiningsaid recess at a location substantially centrally between said oppositeend portions.
 3. The method of claim 2 wherein said recess hasspaced-apart shoulders and said step of forming said flat surface iscarried out forming said flat surface at a location substantiallycentrally between said shoulders to a width less than the distancebetween said shoulders.
 4. The method of claim 1 wherein said workpiececomprises a tool having a cutting body portion integral with saidmounting portion, and further including the step of forming said cuttingbody portion to a diameter less than the diameter of said mountingportion and forming cutting edges on said body portion prior to saidstep of hardening said workpiece.
 5. The method of claim 1 wherein saidstep of finishing said cylindrical mounting portion is carried out bycenterless grinding of said mounting portion to a finished diameterbetween 8 and 14 thousandths greater than the diameter of saidcylindrical recess portion.
 6. The method of claim 1 wherein said stepof finishing said cylindrical mounting portion is carried out bycenterless grinding of said cylindrical portion to a diameter which doesnot deviate from that of a perfect cylinder by more than 0.0005 inch.